Wu hanrong on behalf of YBJ-ASg collaboration

2008.09.24 TeVPA-IV@IHEP

Indirect dark matter search with YBJ-AS Observatory

Outline1. Introduction2. Status of ground-based observations 3. Data analysis with AS experiment4. Results5. Conclusions

Indirect Dark Matter search

From Observation

Gamma-ray flux from WIMP annihilation:

Particle Physics

Astrophysics : Dark matter

halo

Target of indirect search

1. Galactic Halo

2. external galaxies

3. galaxy clusters

4. substructures

5. Galactic Center(GC)

6. Local Group galaxies

7. Mini-spikes around IMBH

Indirect DM search—ground based observatory

IACT arrays

EAS arrays

Advantage: Good angular resolution; gamma/hadron discrimination

Disadvantage: limited FOV and duty cycle

Advantage: large FOV, 90% duty cycle

Disadvantage: no good gamma/hadron identifintification

Data analysis with AS experiment

Tibet AS Observatory

―a.s.l. 4300 m (YBJ , Tibet)―606g/cm2

―Large field of view―Duty cycle (>90%)―Mode Energy: ASγ(~3TeV)

ASγ

ARGO

Run period space Mode EnergyAngular resolution area

Tibet-III 1999.11~2004.10 7.5m ~3TeV ~0.90 ~22050m2

Schematic map of the array and data using in analysis

Tibet-IIIB4

Tibet-II

Statistic (after selection): ~1.86*10^10

analysis method

, on onI N on

on

NI

off

off

NI

, off offI N

Equalon

onoff

NI

N

( , ) ( , )I i j I i j和迭代

全天图以及 M31 显著性

2. No high siginificant point (>5sigma) except known source crab and Mrk421 is detected

1.M31(10.7,41.3)

Non: 2876965

Noff: 2875325.3

Nexc: 1639.7

Significance: 0.97M31

1. 90%C.L. limit— M31

)5.6(1 substr)4.7(2 substr

2. 90%C.L. limit— substructure

-------substructure (>5 )

Significance for BKG Significance for BKG+DM signal

0)5( obsN

2. 90%C.L. limit— substructure

Conclusions

• Detect no any substructure in the field of YBJ ASgamma observatory

• Detect no DM from M31

• 90% C.L. upper limit on “thermally averaged annihilation cross section” between 10^-19cm^3s^-1 and 10^-22cm^3s^-1 is given

• Future search, ARGO-YBJ(~300GeV)

Thanks!

1. 90%C.L. Flux limit— M31

90%C.L. flux limit ：

m

TeVeff

m

TeV

m

TeV

LC

dEEfST

dEEf

dEEf

3.0

1

90%C.L.

1

..%90

)(

)(N

)(

Av

LC

LC

..%90

..%90

DM spectrum

From Observation

Monte Carlo

2. 90%C.L. Flux limit— substructure-----Number of substructure for 800 toy MC trials

0)5( obsN

BKG BKG+DM signal